1. Field of the Invention
Hydrogen is clean energy that does not discharge carbon dioxide even after its combustion, and additionally, its exothermic energy per unit weight is three fold higher than that of petroleum.
Also, hydrogen may be modified into a form of electric energy by its supply into fuel cells.
The present invention relates to a process for the production of hydrogen during the process of treating a variety of substrates, for example, waste water containing highly concentrated organic matter, by using an anaerobic microflora (a group of microorganisms), whereby the present invention serves for the treatment of waste water and hydrogen generation. Therefore, the present invention not only plays an important role in generating hydrogen for the energy industries but also plays an important role industrially for waste water treatment and pollution management.
2. Prior Art
Hydrogen is currently produced by thermal naphtha decomposition or by water electrolysis. Because these processes consume fossil fuel, however, they generally do not serve for improving the global environment. It is also expected that the consumption of fossil fuel will be reduced in the future.
Alternatively, hydrogen generation using microorganisms is grouped into two types; (1) a process employing a photosynthetic microorganism and; (2) a process employing an anaerobic microorganism. The former process, which depends on photosynthetic energy may be complex and inefficient as well as costly. Additionally, the hydrogen generation rate by such microorganisms is slow. Furthermore, the substrate for hydrogen generation is limited. Thus, the former process has a great number of problems, and has not yet been applied in practice (see Yoshimasa Takahara, "Microorganisms contributing to industrial development--Principal role in biotechnology" Hakua Shobo, published Dec. 25, 1983, p. 182-185).
Hydrogen generation by means of anaerobic microorganisms is classified in either the process using a microflora such as digested sludge and lumen bacteria or the process using pure cultures of bacteria; the latter process for waste water treatment is far from reaching a practical stage, because the range of substrate is limited and the process requires sterile conditions, and the like.
On the other hand, in the process which uses a microflora (a mixed population of microorganisms), the microflora can be adapted to a wide variety of substrates without requiring sterile procedures; additionally various waste waters may be used as substrates for hydrogen generation.
Although a number of reports have been published on hydrogen generation by anaerobic microfloras, many of the problems concerning hydrogen productivity and stability are still unsolved.